The present invention relates generally to welding jig apparatus and deals more particularly with a welding jig apparatus for positioning and holding bar stock workpieces in an intersecting and aligned relationship for welding into a metal grating structure.
Metal grating structures of the type comprised of intersecting elements for use with storm water catch basins and the like are generally formed by clamping the elements to a steel topped table which is used as a temporary jig for assembling and welding the elements together into the desired grating. The obvious disadvantages of this procedure are the jig has to be reconstructed each time a new grating is welded and the welding often has to be done in an awkward position. In addition, it is difficult and cumbersome to maintain the elements running in one direction spaced apart and parallel to one another and perpendicular to intersecting elements which also are held spaced apart and parallel to each other.
U.S. Pat. No. 3,815,890 to Urban issued June 11, 1974 discloses a welding jig for positioning and clamping elements of a grating structure wherein the jig and clamped grating elements are rotatable in the vertical plane to improve welding access to the intersecting elements forming the grating structure. One drawback to the welding jig disclosed by Urban is that the support frame must be in the vertical plane with the lateral frame members generally parallel to the ground surface so that support pins located on pin supporting bars transversely mounted between the lateral frame members provide a surface upon which the elements are rested prior to clamping. The grating side members are then manually clamped to the spaced apart grating elements in readiness for welding. Although the Urban welding jig facilitates the assembly and welding of a grating structure in comparison to prior methods and techniques, the jig is not completely satisfactory. Twisting screw clamps are manually operated and are used to hold the grating elements in position and to the welding jig. The placement of the grating elements in the desired position on the supporting pins and the manual clamping required by the Urban welding jig is time consuming and in the case of repetitive manufacture of grating structures, the time consumed in the placement and clamping of the grating elements can become excessive over the course of a working day. In addition, the grating elements are susceptible to being knocked off the support pins during the placement of other elements on the jig.
A general object of this invention therefore, is to provide a welding jig apparatus for positioning and holding bar stock workpieces in an intersecting and aligned relationship for manufacturing metal grating structures.
Another object of the invention is to provide a welding apparatus which automatically and accurately clamps bar stock workpieces into the desired aligned relationship and parallel to one another substantially eliminating the possibility of misalignment.
A further object of this invention is to provide a tiltable welding jig apparatus for positioning the bar stock workpieces in one of a number of positions for welding.